Smallest possible orbital rocket

[sevenperforce]

As you scale down rockets, the atmosphere becomes "thicker" from the rocket's point of view, to the point that it would eventually become impossible to achieve orbit.

If some hobbyists got together and pooled their resources, what's the smallest possible rocket that could actually reach orbit? Staging allowed; no payload required other than aeroshell and engines.

[Exploro]

To hazard a guess; the initial vehicle mass would be around 10 metric tons.

Edited February 16, 2016 by Exploro

[Nibb31]

It would probably be close to the early orbital rockets like the Juno I or the french Diamant.

[jf0]

Under 10t is feasible, this one took 26kg to orbit https://en.wikipedia.org/wiki/Lambda_4S

[PB666]

2 hours ago, sevenperforce said:

As you scale down rockets, the atmosphere becomes "thicker" from the rocket's point of view, to the point that it would eventually become impossible to achieve orbit.

If some hobbyists got together and pooled their resources, what's the smallest possible rocket that could actually reach orbit? Staging allowed; no payload required other than aeroshell and engines.

Take it up to Pikes peak and launch it. Probably the best place in on a equitorial mountain midday during spring or fall (air temperatures are the hottest, increases Mach and delays the sonic boom). If you can launch above 10,000 feet, air thins rather rapidly, above 18000 feet your in commercial jet aircraft range, so.

The problem with the lamda design that I see, the diameter of the rocket severly limits the type of payloads to compact devices that need to do alot of unfolding to work.

[fredinno]

2 hours ago, PB666 said:

Take it up to Pikes peak and launch it. Probably the best place in on a equitorial mountain midday during spring or fall (air temperatures are the hottest, increases Mach and delays the sonic boom). If you can launch above 10,000 feet, air thins rather rapidly, above 18000 feet your in commercial jet aircraft range, so.

The problem with the lamda design that I see, the diameter of the rocket severly limits the type of payloads to compact devices that need to do alot of unfolding to work.

A ground-Launched Pegasus has higher diameter, and can launch similar payloads (though it is heavier due to its inefficent first stage.)

[sevenperforce]

What if you go even smaller? No payload at all, minimal avionics, smallest possible terminal stage. 

[DerekL1963]

3 hours ago, Nibb31 said:

It would probably be close to the early orbital rockets like the Juno I or the french Diamant.

Smaller though.  We can build much lighter structures, have more efficient engines, and the guidance system and electronics (which have to be carried most of the way even in an Explorer I configuration) are orders of magnitude lighter.

[Exploro]

7 hours ago, PB666 said:

TThe problem with the lamda design that I see, the diameter of the rocket severly limits the type of payloads to compact devices that need to do alot of unfolding to work.

Considering OP's parameter, payload was not of terrible concern; the rocket needed only insert itself and it's motor into LEO.

[fredinno]

4 hours ago, DerekL1963 said:

Smaller though.  We can build much lighter structures, have more efficient engines, and the guidance system and electronics (which have to be carried most of the way even in an Explorer I configuration) are orders of magnitude lighter.

Can we do air-launch too? That might reduce the size to less than 5 T.

[DerekL1963]

Just now, fredinno said:

Can we do air-launch too? That might reduce the size to less than 5 T.

If you want to significantly increase the cost, sure.   Landbased pads, especially for a vehicle this size, are cheap, cheap, cheap.   (Basically a square of concrete and a smallish rolling building.)   Custom modified aircraft... are not.

[Rakaydos]

3 minutes ago, DerekL1963 said:

If you want to significantly increase the cost, sure.   Landbased pads, especially for a vehicle this size, are cheap, cheap, cheap.   (Basically a square of concrete and a smallish rolling building.)   Custom modified aircraft... are not.

Unless, of course, you size it to fit a "standard" hardpoint, so customizing the aircraft is unnessisary.

The F14 is known to fire the AIM 54 Phoenix missile which is about 1000 pounds. (450-470 KG)

The F14 had a service cealing of 15 KM, and a top speed of mach 2.3 at high altitude.

Can you design an airlaunched anti-sat missile under 450 KG, with at least that kind of airlaunch performance?

[DerekL1963]

20 minutes ago, Rakaydos said:

Unless, of course, you size it to fit a "standard" hardpoint, so customizing the aircraft is unnessisary.

The F14 is known to fire the AIM 54 Phoenix missile which is about 1000 pounds. (450-470 KG)

The F14 had a service cealing of 15 KM, and a top speed of mach 2.3 at high altitude.

Can you design an airlaunched anti-sat missile under 450 KG, with at least that kind of airlaunch performance?

The specification is a hobbyist launcher - private citizens don't have access to F14's, even if it were still in service.  (It isn't.)  Even if they did, it's a very expensive aircraft to operate.

[Nothalogh]

11 hours ago, sevenperforce said:

As you scale down rockets, the atmosphere becomes "thicker" from the rocket's point of view, to the point that it would eventually become impossible to achieve orbit.

If some hobbyists got together and pooled their resources, what's the smallest possible rocket that could actually reach orbit? Staging allowed; no payload required other than aeroshell and engines.

Air augmentation is your friend, in this situation, see the soviet Gnom

[fredinno]

59 minutes ago, DerekL1963 said:

The specification is a hobbyist launcher - private citizens don't have access to F14's, even if it were still in service.  (It isn't.)  Even if they did, it's a very expensive aircraft to operate.

We can just put it on one of Virgin Galactic's WhiteKnight2s then!

[Rakaydos]

Or the first whiteknight, if we can scale it down enough...

[fredinno]

1 minute ago, Rakaydos said:

Or the first whiteknight, if we can scale it down enough...

That plane was retired tho.

[wumpus]

I take it nobody here reads El Reg?  They have a long on-going LOHAN (Low Orbit Helium Assisted Navigator) balloon launched "spaceplane" project.  Best guess is that they are going for "touching the Karman line" instead of orbit (at least on this second flight, I think the first had ignition issues).  Note that the project is stalled due to FAA approval (since this is a UK project, they tried to get EU approval first.   Not a chance).  No word on what hoops Ecuador would ask you to jump through.

Checking Amazon.com for weather balloons indicates a ~120,000' (36km) flight ceiling (three times what Pegasus uses), but minimal load per balloon.  Design improvements include no need for non-vacuum bell design, no need for low TWR design (unfortunately low weight requirements interfere with a bunch of SRB tricks learned in KSP & forums).

http://www.theregister.co.uk/science/lohan

[magnemoe]

20 minutes ago, wumpus said:

I take it nobody here reads El Reg?  They have a long on-going LOHAN (Low Orbit Helium Assisted Navigator) balloon launched "spaceplane" project.  Best guess is that they are going for "touching the Karman line" instead of orbit (at least on this second flight, I think the first had ignition issues).  Note that the project is stalled due to FAA approval (since this is a UK project, they tried to get EU approval first.   Not a chance).  No word on what hoops Ecuador would ask you to jump through.

Checking Amazon.com for weather balloons indicates a ~120,000' (36km) flight ceiling (three times what Pegasus uses), but minimal load per balloon.  Design improvements include no need for non-vacuum bell design, no need for low TWR design (unfortunately low weight requirements interfere with a bunch of SRB tricks learned in KSP & forums).

http://www.theregister.co.uk/science/lohan

They can always launch from an ship, however reaching 100 km is way simpler than orbit: compare Falcon 9 and new Shepard. 
Standard missile 3 was able to intercept an satellite in low orbit https://en.wikipedia.org/wiki/RIM-161_Standard_Missile_3 it weight 6.5 tons but has lots of extra heavy features and is solid fuel.. 

https://en.wikipedia.org/wiki/Civilian_Space_eXploration_Team
amateurs has managed this too. 

Plane drop would reduce the weight reaching orbit so much its probably smart to add plane features to the rocket, think an jet engine like the one on cruise missiles and an wing 
jet engine with its fuel and the wing will be booster stage taking it to 10 km or higher this separates and first stage starts. Upper stage might be solid because it has to be small with low dry mass, an solid rocket would be an tube with some flight control systems.

[sevenperforce]

Let's say a multistage, ground-launched solid-fueled rocket. How small can the terminal orbital insertion stage be?

[Nothalogh]

2 hours ago, sevenperforce said:

Let's say a multistage, ground-launched solid-fueled rocket. How small can the terminal orbital insertion stage be?

With air augmented first stage, and no real concern for g forces, I'd suspect around 15 tons on the pad.

Only downside to going small is that one can't climb slowly into the gravity turn, this is gonna almost look like a Nike Sprint launch 

[sevenperforce]

How many stages? At what point does the addition of more stages result in diminished performance? Would the final upper stage be the size of a pool noodle? A paper towel tube? A pencil?

[ElWanderer]

This thread reminded me of this xkcd what-if: https://what-if.xkcd.com/24/

[wumpus]

1 hour ago, Nothalogh said:

With air augmented first stage, and no real concern for g forces, I'd suspect around 15 tons on the pad.

Only downside to going small is that one can't climb slowly into the gravity turn, this is gonna almost look like a Nike Sprint launch 

Air augmenting 15 tons of rocket?  That's easily 20 American-sized passengers.  You would need something similar to the things (B-52, L-1011) Orbital uses to loft the 18 ton Pegasus.  Or by "air augmenting" do you mean adding something like ramjet boosters, or possibly a hybrid with an air inlet?

You could get most of the effect (and equatorial delta-v) by launching from Pichincha (a mountain next to Ecuador's capital) [4.7km high].  You could try a similar effect near Leadville, CO (two mile high city), but need more delta-v than other US launch pads (roughly equal to Wallops).

As a comparison, the CSXT "GoFast" massed 350kg and had a 18kg payload.  I'd have to assume that it had considerable aero losses (thus the name), although it launched in Denver, CO (note: for those who've never been there.  Denver is still on the plains right next to the Rocky Mountains (expect flatland if staying there, extreme mountains if even slightly west of Denver).  Presumably they didn't have clearance for finding higher elevation).

[Nothalogh]

44 minutes ago, wumpus said:

Air augmenting 15 tons of rocket?  That's easily 20 American-sized passengers.  You would need something similar to the things (B-52, L-1011) Orbital uses to loft the 18 ton Pegasus.  Or by "air augmenting" do you mean adding something like ramjet boosters, or possibly a hybrid with an air inlet?

 

I mean an air augmented rocket, as in the Soviet Gnom missile or the MDBA Meteor.

Also known as a ramrocket, a ducted rocket, or a rocket ejector